Leeuwenburgh C. Apoptosis in skeletal muscle with aging

copenia may be partly due to a loss in total fiber number by apoptosis. We have investigated age-related alterations in the mitochondria-mediated pathway leading to apoptosis in the gastrocnemius muscle from 6-mo-old and 24-mo-old male Fisher 344 rats. Apoptosis (mono- and oligonucleosome frag-mentation) in the gastrocnemius muscle was increased by 50 % in the old rats compared with the adult animals. Fur-thermore, there was a significant correlation between cyto-solic cytochrome c and caspase-3 activity, although neither cytochrome c nor caspase-3 activity increased significantly with age. Furthermore, there was a significant correlation between caspase-3 activity and mono- and oligonucleosome fragmentation in the old rats only. Mitochondrial Bcl-2 and Bax were not altered with age. In vitro experiments demon-strated that activation of the caspase cascade in skeleta